Abidjan, Ivory Coast (CNN) -- The African Union chief flew to Ivory Coast on Saturday to make another attempt to resolve the crisis there amid a slaughter of women protesters blamed on self-proclaimed President Laurent Gbagbo.

A video posted online documented in chilling, graphic detail the transformation Thursday of a peaceful demonstration in the city of Abidjan into grisly killings by what appear to be forces loyal to Gbagbo.

U.S. officials said the attack left seven women dead, but Gbagbo rival Alassane Ouattara put the death toll at 12, including a child, with 110 more people wounded.

The video was broadcast widely on opposition television in Ivory Coast. CNN staffers familiar with Abidjan said the video appeared to have been recorded in the city's restive Abobo suburb.

Gbagbo denied his forces were behind the killings and instead charged a "gross manipulation" of events. State television aired Saturday another video, which also appeared to be shot in Abobo, of armed protesters, and suggested that Ouattara's supporters were responsible for the deaths.

The international community has called on Gbagbo to end his siege on his challenger, Alassane Ouattara, widely recognized as the legitimate president, and appealed for an end to the escalating violence in the west African nation.

Jean Ping, chairman of the African Union (AU) commission was expected to meet with both Gbagbo and Ouattara and formally invite both men to the next meeting of the heads of state panel, said AU representative Ambroise Nyonsaba.

That panel called Friday for "an immediate end to killings and abuses that led to the loss of human lives, as well as demonstrations, marches and other activities likely to degenerate into disturbances and violence."

An eight-minute video posted on YouTube showed hundreds of people, most of them women dressed in brightly colored garb, smiling, chanting, playing horns, blowing whistles and dancing.

Many of them carried signs with slogans written in French that referred to Gbagbo as "assassin" and "robber of power." One of them held a poster declaring Ouattara, as president. None of them appeared to be carrying a weapon.

Dark clouds hung low, harbingers of what happens next.

The chanting stopped, replaced by an eerie quiet, as the jittery hand-held camera turned away from the crowd and focused on the approach of a convoy of three camouflage-painted armored vehicles, one of them bearing the word "Police."

Without any apparent warning, a volley of three bursts from a heavy-caliber gun pierced the quiet, followed by screams as the marchers, including whoever is holding the camera, run from the street, leaving behind pavement littered with flip-flops, clothing and tote bags.

To a soundtrack of wailing, the camera then made its way toward individual mounds of flesh on the pavement, each steeped in a pool of red.

One woman appeared to have been decapitated; another suffered a deep wound in the neck; yet another, a deep wound in the back, her torso soaked in blood, tried to raise her head from the pavement but lowered herself back down.

A spokesman for Gbagbo, Sylvere Nebout, said in a telephone interview that he knew nothing about the video, but added that this was "as usual, a manipulation from the opposition."

He forwarded a statement from army spokesman Col. Hilaire Babri Gohourou, which aired Friday night on television. It denied involvement of defense and security forces.

"These charges are necessarily false and without any ground," he said, adding that no security and defense forces had been in the Abobo area Thursday.

Youssoufou Bamba, the United Nations ambassador to Ivory Coast and a Ouattara supporter, said he was in shock.

"Having watched that video now, I'm quite depressed," he said.

He accused Gbagbo -- a Christian from the south -- of seeking to foment the nation's descent toward civil war.

"Actually, he's conducting an ethnic cleansing because the people who have been killed have been killed along ethnic lines," Bamba said, referring to the mostly Muslim people from the northern and central parts of the country and from neighboring countries.

He called for the United Nations to be given "a robust mandate" for its peacekeeping operation in the country. And the Economic Community of West African States, or ECOWAS, should step in and protect the civilians," Bamba said. "Otherwise, as long as this crisis lasts, people will be killed." He put the death toll in the past three months at 600.

The United Nations has said that at least 365 people have been killed since the crisis started in December. Another 200,000 people have been displaced by the bloodshed.

The U.N. refugee agency said it was increasingly more difficult for humanitarian organizations to reach people who have fled Abobo for safer areas of Abidjan as well as the needy in the western part of the country near the Liberian border.

The unrest began in after a disputed late-November election that left both Gbagbo and Ouattara claiming victory. Since then, Ouattara has been working from a hotel and has been protected by U.N. peacekeepers.